1. Field of the Invention
The present invention relates to a driving device, and more particularly to a driving device that drives actuators installed in a vehicle such as an automobile.
2. Description of the Related Art
Important initiatives have been undertaken in recent years to standardize the functional safety of electrical equipment and electronic devices installed in automobiles. Rigorous assessment in terms of defining faults in mounted electronic components, clarifying fault determination criteria, and addressing the faults applies also to electronic control units (ECUs) that control power trains. The demands placed also on responsiveness to such faults are likewise stringent.
As system complexity increases, the targets of fault determination become more numerous, and fault determination requirements become likewise more complex. The processing load of the ECU and the communication traffic between the ECU and associated devices increase as a result.
Herein, the term “power train” denotes an apparatus for efficiently transmitting rotational energy, generated by an engine, to tires. The power train includes a clutch, a transmission, a propeller shaft, a differential gear and a drive shaft.
A system control device disclosed in Japanese Patent Application Publication No. H7-43257 is made up of two chips, namely a host-side unit and a sub-side unit. The host-side unit has a host processor that performs main system control. The sub-side unit has a subprocessor that performs subsidiary system control, and a standby system processor that performs system control occasionally when an abnormality occurs. The host processor and the subprocessor operate according to a first clock, and the standby system processor operates according to a second clock. The host processor, the subprocessor and the standby system processor each have a fault self-determination execution circuit. The fault self-determination execution circuits of the host processor and of the subprocessor perform fault determination using the second clock, while the fault self-determination execution circuit of the standby system processor performs fault determination using the first clock. Japanese Patent Application Publication No. H7-43257 discloses the feature of securing a reliable fail-safe function by using different clock system in the standby system processor alone.
A vehicular electronic control device disclosed in Japanese Patent Application Publication No. 2014-046730 is provided with a driver IC and a microcontroller. The microcontroller inputs a diagnosis start signal to the driver IC, via serial communication. Upon reception of the diagnosis start signal, the driver IC reads, from a ROM, the ON/OFF state of each driver circuit, in a group of registers. Each driver diagnosis circuit performs then diagnosis upon turn-on/off, according to the values of the registers. Drive circuits detected to be faulty as a result of the diagnosis are brought to an inactive state, and the microcontroller is notified of the fact.
The load drive device disclosed in Japanese Patent Application Publication No. 2009-077542 is built into an electronic control device. The load drive device drives a load such as a solenoid. The load drive device is provided with a drive circuit and a diagnosis circuit. The diagnosis circuit diagnoses the state of the load. The diagnosis circuit operates upon system initialization or while the drive circuit is stopped. The drive circuit stops when a drive-stop signal is inputted to the electronic control device, from a control circuit that controls the drive circuit. The normal operation of the diagnosis circuit is thus checked in a state where the load drive device remains built into the electronic control device.